You are here

Rockwool RW5 Vs RW3

Customising, building or repairing your own gear? Need help with acoustic treatment or soundproofing? Ask away…

Re: Rockwool RW5 Vs RW3

Postby Sam Spoons » Wed Aug 19, 2020 9:30 pm

With a cut edge facing the front rather than a treated flat surface. It's achieved by stacking triangular pieces with the long edge across a corner rather than standing a panel vertically in the corner and filling the void. Only really used for bass traps as broadband absorbers made up with, say 50 or 100mm panels of RW3 are probably a little less efficient but, in the real world, work just fine.
User avatar
Sam Spoons
Jedi Poster
Posts: 13406
Joined: Thu Jan 23, 2003 1:00 am
Location: Manchester UK
Finally taking this recording lark seriously (and recording my Gypsy Jazz CD)........

Re: Rockwool RW5 Vs RW3

Postby shufflebeat » Wed Aug 19, 2020 10:02 pm

Wary of derailing but would like to explore this idea further if anyone can spare a moment.

https://www.soundonsound.com/forum/view ... 35#p705835
shufflebeat
Jedi Poster
Posts: 5044
Joined: Sun Dec 09, 2007 1:00 am
Location: Manchester, UK
"Dance, dance. wherever you may be, for I am the Lord of the damp settee..."

Do yourself a favour, wear earplugs at gigs.

Re: Rockwool RW5 Vs RW3

Postby eoinw » Thu Aug 20, 2020 2:49 pm

blinddrew wrote:
eoinw wrote:Hello Gnome. Thanks for your knowledge. I would appreciate it very much if you could offer some guidance on my situation.

I am building bass traps like the ones in this video :

https://youtu.be/41liBn-QNW4?t=690

but my dimensions will be a little different. My triangle will measure 15" x 15" x 21.2" (38.1 cm x 38.1 cm x 53.8 cm) and the traps will be 24" high (70 cm high)

Having read your comments I am guessing that 100 kg/m3 RW5 would be a bad choice for these traps as I would get more reflection than absorption. Is this correct? Would you advise me to go for 60 kg/m3 RW3 instead?

Thanks
Even end-on 100kg is going to be quite reflective.


Are you sure about this? What are you basing this on? I've checked this with some experts, one of whom is a grammy winning mastering engineer, and they told me the idea that higher density rock wool becomes reflective when you use it in deeper/thicker panels and traps is a myth. They say that RW5 is the best.
eoinw
Posts: 3
Joined: Wed Aug 19, 2020 1:35 pm

Re: Rockwool RW5 Vs RW3

Postby Sam Spoons » Thu Aug 20, 2020 4:01 pm

Sources?

The cut edges of rockwool panels have a lower acoustic impedance because the are less dense in the centre of the thickness and because the faces of the panel are less permeable (this may simply be due to the manufacturing process or some kind of treatment, I don't know).
User avatar
Sam Spoons
Jedi Poster
Posts: 13406
Joined: Thu Jan 23, 2003 1:00 am
Location: Manchester UK
Finally taking this recording lark seriously (and recording my Gypsy Jazz CD)........

Re: Rockwool RW5 Vs RW3

Postby James Perrett » Thu Aug 20, 2020 9:40 pm

eoinw wrote:I've checked this with some experts, one of whom is a grammy winning mastering engineer...

I wouldn't trust a Grammy winning mastering engineer to be an acoustic materials expert - in the same way as I wouldn't expect an acoustic materials expert to be an expert mastering engineer. Occasionally you may find someone with expertise in both fields but it would be rare.
User avatar
James Perrett
Moderator
Posts: 9694
Joined: Mon Sep 10, 2001 12:00 am
Location: The wilds of Hampshire
JRP Music - Audio Mastering and Restoration. JRP Music Facebook Page

Re: Rockwool RW5 Vs RW3

Postby Hugh Robjohns » Thu Aug 20, 2020 10:22 pm

eoinw wrote:Are you sure about this? What are you basing this on? I've checked this with some experts, one of whom is a grammy winning mastering engineer, and they told me the idea that higher density rock wool becomes reflective when you use it in deeper/thicker panels and traps is a myth. They say that RW5 is the best.

The trouble with the topic of acoustics is there are so many ways of achieving much the same end result, and so naturally different people have their own ideas about what you absolutely must or must not do or use...

At the end of the day, though, any acoustic installation is really about the total sum of all the different parts, and not just one or two individual elements. So you can build traps with RW5 if you want, but you might end up having to design and install other or additional treatment elsewhere to compensate for some of its specific acoustic characteristics...just as you would with different additional elements if you used RW3 or something else.

Max (...Gnome) has given -- in this and other posts in this forum -- several explanations as to the various pros, cons and practicalities of using different densities of mineral wools for different purposes. His way of doing things is the way he does them because he knows it works and it's practical for him to implement to budget and specification. Other acousticians might choose a different method... But still get the same overall results.

Personally, I'd place more weight on the advice of someone with a proven track record of physically building and measuring working studios as a professional business, over someone who's paid someone else to build a room for them... possibly... :)

But if you're not paying for the words of advice you're receiving, they're all really just opinions... So pick and choose the ones that fit with your own detiled technical research or your personal belief regime... Whichever is the easier.
User avatar
Hugh Robjohns
Moderator
Posts: 28361
Joined: Fri Jul 25, 2003 12:00 am
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: Rockwool RW5 Vs RW3

Postby Mixedup » Fri Aug 21, 2020 10:46 am

I'd second (third, fourth?) the recommendation of using 'side-on' RW3 (60kg/m3) in home studio acoustics.

It's just SO MUCH easier to work with than RWA45 (45/m3) — you can easily cut neatly to fit with a bread knife and it retains its structural integrity, so while it's heavier, practical experience suggests that it actually requires less by way of supporting frames and so on.

RW5 (100kg/m3) is denser and sturdier still, but at a cost acoustically... I've used that in the past, thinking 'denser = better LF absorption' and it's a mistake; things can start to sound a touch 'boxy', and I've found I need to add something less dense in front of it for it to be of much use for acoustics (Great used in walls for soundproofing, mind, and again, very easy to cut).
User avatar
Mixedup
Jedi Poster
Posts: 4414
Joined: Wed Sep 03, 2003 12:00 am
Location: Cambridgeshire, UK

Re: Rockwool RW5 Vs RW3

Postby DanDan » Sat Aug 22, 2020 8:14 pm

Semi rigid fibre batt traps are extremely good bang per buck. In the old studiotips.com lab measurements, with extrapolation, the 60cm wide corner straddlers bigly outperform the much larger fully filled SuperChunks and Megalenrds. http://forum.studiotips.com/viewtopic.php?f=8&t=536 IMO this is likely due to a damped resonant membrane effect. This seems more likely with fibreglass vs RW and with higher densities. Floppy batts don't boom.
Testing trumps theory in my world, here's another example.
http://ethanwiner.com/density.html

So all of that plus potential sagging make it seem no wonder that pretty much all manufacturers used 100KG. Of late some have dropped to as low 600KG which must be much cheaper, but is Knauf Ecose Earthwool the same as Rockwool? Is it a technical or a profit improvement? I think a bit of both. But I also think that at 3-3.5inches and up to say 5 or 6, 100KG RW or Ecose, or 705 are the best choices.
So much for the old world. My current preferred fibre is Polyester which seems to have great absorption and rigidity at quite low densities. It also fire retardant and does not need a containment or cosmetic layer of fabric. I would go so far as to recommend it AS the containment and cosmetic layer for very much deeper traps of cheap low density fibre.
User avatar
DanDan
Regular
Posts: 66
Joined: Tue Feb 10, 2009 1:00 am
Location: Cork Ireland
Dan FitzGerald MIOA  MAES
www.irishacoustics.com
www.soundsound.ie

Re: Rockwool RW5 Vs RW3

Postby Studio Support Gnome » Thu Sep 03, 2020 12:10 am

DanDan wrote:So much for the old world. My current preferred fibre is Polyester which seems to have great absorption and rigidity at quite low densities. It also fire retardant and does not need a containment or cosmetic layer of fabric. I would go so far as to recommend it AS the containment and cosmetic layer for very much deeper traps of cheap low density fibre.


I Have also largely moved to Poly core board for a lot of my panels (when I do anything at all these days ) but it's not cost effective for large absorption mass designs .it's available in the Uk from EQ acoustics. and I highly recommend it .... it comes in pure white, and now I believe they're starting to do grey and black also, and you can absolutely get away without fabric covering.... they have a version with a fine enough front surface to print on..... and for large panels it's a dream to work with . needs a VERY sharp knife to cut cleanly ...... (and everyone who's been anywhere near me on a build knows i have a very large , very sharp, (Psycho) knife .... not quite in to reaper man field of ultimate sharpness territory, but i'm working on it )

I should also point out to Dan, that the critical difference not implemented in those tests , is edge facing use of the material..... they had flat faced with rear in-fill and the materials were quite different . I was building bass traps like this in the late 80's ..... before the internet really existed.....

Sorry not to have replied to individual questions, I'm a tad busy designing heat recovery systems and getting MCS certified for Air and Ground source heat pump technologies ..... new job, new toys to play with, and very very busy......
User avatar
Studio Support Gnome
Frequent Poster (Level2)
Posts: 2921
Joined: Tue Jul 22, 2003 12:00 am
Location: UK
Mostly Retired from Audio.... If I already know you I'll help,  if not....    Ask Hugh Robjohns, unless that is you're in need of 80's shred guitar... that, I'm still interested in having fun with...

Previous